Bubble jet printing, also known as thermal ink jet printing, is often accomplished by heating fluid in a firing chamber. Typically, there are many firing chambers situated upon a semiconductor chip. The heated ink in each firing chamber forms a bubble. Formation of the bubble forces the heated ink out of a nozzle or orifice associated with the firing chamber towards a medium in a thermal ink jet printing operation. One common configuration of a thermal ink jet printhead is often called a roof shooter-type thermal ink jet printhead because the ink drop is ejected in a direction perpendicular to the plane of the thin films and substrate that comprise the semiconductor chip.
Often, a resistor on the die heats the fluid in the firing chamber. The resistor is typically heated by electrical resistance heating. Electrical contacts are formed over the die and electrically coupled with conductor traces that coordinate pulsed delivery of electrical power to the resistor for a predetermined time. The electrical contacts are often formed of gold.
The material that defines the firing chamber is often organic. This organic material is typically deposited over a cavitation barrier layer, that is typically over a passivation layer over the resistor. In some instances, the organic material does not adhere to or becomes detached from the thin film layers over the die. For instance, repeated impact from the collapsing numerous bubbles can cause the organic material to become detached. When cracks are present in the thin film layers beneath, the electrically conductive ink can flow through the cracks or breaks and open up a passageway therebeneath. When the ink contacts underlying electrically conductive layers, the ink will corrode the conductive layers, resulting in increased resistance and eventual resistor failure. In severe cases an entire power supply bus may be corroded resulting in several resistors on a printhead failing. Accordingly, it is desired to protect the conductor traces from ink corrosion and to provide good adhesion of the material forming the firing chamber.
Additionally, gold often does not adhere well to some materials. In particular, gold often does not adhere well to the material forming the firing chamber. Therefore, it is desirable to identify materials that adhere well to gold, as well as the material forming the firing chamber.
In one embodiment, a fluid ejection device includes a substrate with a fluid drop generator, wherein the fluid drop generator is top coated with a first barrier layer. The device also has a second barrier layer substantially defining a chamber about the fluid drop generator, and at least one layer deposited in between the first and second barrier layers.
These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.